Polycarbonate compositions

ABSTRACT

The present invention is concerned with ternary polycarbonate compositions having improved impact strength. The ternary compositions comprise a mixture of thermoplastic, aromatic polycarbonates which are derived from aromatic dihydroxy compounds, an acrylate copolymer and a polyolefin and its oxide.

This application is a continuation-in-part of copending application Ser.No. 69,825 filed Aug. 27, 1979 now U.S. Pat. No. 4,245,058.

The present invention relates to improving both the aged impact strengthand the low temperature impact strength of high molecular weight,aromatic polycarbonate resins.

BACKGROUND OF THE INVENTION

It is well known that polycarbonate resins have high impact strengthbelow a critical thickness of between about 1/2 and 1/4 inches. Abovethis average thickness the impact strength of polycarbonate resins islow. Additionally, the impact strength of polycarbonate resins decreasesrapidly as temperatures decrease below about -5° C. and also after agingthe polymers at elevated temperatures above about 100° C. Thesecharacteristics consequently limit the fields of applications of theseresins. Thus, unmodified polycarbonate materials are not practical foruse at low or high temperatures when good impact strength is required.Therefore, it is desirable to improve both the impact strength ofpolycarbonate resins at low and high temperatures and their aged impactstrength to thereby expand the fields of application of such resins.

DESCRIPTION OF THE INVENTION

It has now been discovered that ternary compositions, which comprise ahigh molecular weight, thermoplastic, aromatic polycarbonate, anacrylate copolymer and a polyolefin, exhibit not only improved agedimpact strength, but certain formulations thereof also exhibit improvedimpact strength at both low and high temperatures when compared tounmodified polycarbonate resins. These novel compositions also exhibitgood weld-line strength.

High molecular weight, thermoplastic, aromatic polycarbonates in thesense of the present invention are to be understood ashomopolycarbonates and copolycarbonates and mixtures thereof which haveaverage molecular weights of about 8,000 to more than 200,000 preferablyof about 20,000 to 80,000 and an I.V. of 0.40 to 1.0 dl/g as measured inmethylene chloride at 25° C. These polycarbonates are derived fromdihydric phenols such as, for example, 2,2-bis(4-hydroxyphenyl)propane,bis(4-hydroxyphenyl)methane, 2,2-bis(4-hydroxy-3-methylphenyl)propane,4,4-bis(4-hydroxyphenyl)heptane,2,2-(3,5,3',5'-tetrachloro-4,4'-dihydroxyphenyl)propane,2,2-(3,5,3',5'-tetrabromo-4,4'-dihydroxydiphenyl)propane, and(3,3'-dichloro-4,4'-dihydroxydiphenyl)methane. Other dihydric phenolswhich are also suitable for use in the preparation of the abovepolycarbonates are disclosed in U.S. Pat. Nos. 2,999,835; 3,038,365;3,334,154; and 4,131,575.

These aromatic polycarbonates can be manufactured by known processes,such as, for example, by reacting a dihydric phenol with a carbonateprecursor such as phosgene in accordance with methods set forth in theabove-cited literature and U.S. Pat. Nos. 4,018,750 and 4,123,436, or bytransesterification processes such as are disclosed in U.S. Pat. No.3,153,008, as well as other processes known to those skilled in the art.

The aromatic polycarbonates utilized in the present invention alsoinclude the polymeric derivates of a dihydric phenol, a dicarboxylicacid, and carbonic acid, such as are disclosed in U.S. Pat. No.3,169,131.

It is also possible to employ two or more different dihydric phenols ora copolymer of a dihydric phenol with a glycol or with hydroxy or acidterminated polyester, or with a dibasic acid in the event a carbonatecopolymer or interpolymer rather than a homopolymer is desired for usein the preparation of the aromatic polycarbonate utilized in thepractice of this invention. Also employed in the practice of thisinvention can be blends of any of the above materials to provide thearomatic polycarbonate.

Branched polycarbonates, such as are described in U.S. Pat. No.4,001,184, can also be utilized in the practice of this invention, ascan blends of a linear polycarbonate and a branched polycarbonate.

The "acrylate" copolymer utilized in the present invention is acopolymer of a C₁ -C₅ methacrylate and a C₁ -C₅ acrylate, wherein theterm "C₁ -C₅ " represents both saturated and unsaturated, straight orbranched chained aliphatic hydrocarbon radicals having from 1 to 5carbon atoms.

Preferred acrylates for use in the copolymer are methyl acrylate, ethylacrylate, isobutyl acrylate, 1,4-butanediol diacrylate, n-butylacrylate, and 1,3-butylene diacrylate. Preferred methacrylates for usein this copolymer include methyl methacrylate, isobutyl methacrylate,1,3-butylene dimethacrylate, butyl methacrylate and ethyl methacrylate.

The acrylate portion of the copolymer, based on the total weight of thecopolymer, can range from about 50 to about 85 weight percent. Themethacrylate portion of the copolymer can range from about 15 to about50 weight percent.

The preferred acrylate copolymer for use in this invention is acopolymer of n-butyl acrylate and methyl methacrylate in which theweight ratio of the n-butyl acrylate fraction to the methyl methacrylatefraction in the copolymer is about 3 to 2.

Suitable acrylate copolymers, as defined above, can be prepared bymethods well known to those skilled in the art or can be obtainedcommercially. For example, Rohm and Haas' Acryloid® KM 330 copolymer,which is a copolymer of n-butyl acrylate and methyl methacrylate, issuitable for use in the present invention.

Suitable polyolefins for use in the present invention include, forexample, polyethylene, polypropylene, polyisobutylene, ethylenepropylene diene copolymer, and their oxides, copolymers and terpolymers.Additional polyolefins suitable for use herein will be apparent to thoseskilled in the art. The preferred polyolefins are polyethylene andpolypropylene. These polyolefins and their oxides, co- and terpolymersare available commercially.

The amount of the polyolefin present in the ternary composition of thepresent invention can range from about 0.5 to about 4 parts, by weight,per hundred parts of the aromatic polycarbonate. Preferably, thepolyolefin is present in amounts of from about 1 to about 3 parts, byweight, per hundred parts of the aromatic polycarbonate. The amount ofthe acrylate copolymer present in the ternary composition can vary fromabout 2 to about 6 parts, by weight, per hundred parts of the aromaticpolycarbonate. Preferably, the acrylate copolymer is present in amountsof from about 3 to about 5 parts, by weight, per hundred parts of thearomatic polycarbonate.

It is also regarded to be among the features of this invention toinclude in the ternary polycarbonate composition conventional additivesfor purposes such as reinforcing, coloring or stabilizing thecomposition in conventional amounts.

The compositions of the invention are prepared by mechanically blendingthe high molecular weight aromatic polycarbonate with the acrylatecopolymer and the polyolefin by conventional methods.

EXAMPLES

The following examples are set forth to illustrate the invention and arenot to be construed to limit the scope of the invention. In the examplesand comparative studies, all parts and percentages are on a weight basisunless otherwise specified.

EXAMPLE 1

Ninety-five (95) parts of an aromatic polycarbonate, derived from2,2-bis(4-hydroxyphenyl)propane and having an intrinsic viscosity (I.V.)in the range of from about 0.46 to about 0.49 dl/g as determined inmethylene chloride solution at 25° C., was mixed with four (4) parts ofa copolymer of n-butyl acrylate and methyl methacrylate (hereinafteracrylate copolymer), said copolymer having a weight ratio ofn-butyl-acrylate to methyl methacrylate of about 3 to 2, and one (1)part of polypropylene. The ingredients were then blended together bymechanically mixing them in a laboratory tumbler and the resultingmixture was fed to an extruder which was operated at about 265° C. Theresulting extrudate was comminuted into pellets. The pellets wereinjection molded at about 290° C. to 310° C. into test specimens ofabout 5" by 1/2" by 1/4" and 5" by 1/2" by 1/8", the latter dimensionbeing the specimen thickness. Izod impact strengths of these specimensare measured according to the notched Izod test, ASTM D256, and are setforth in Table I. The ductile-brittle transition temperature (D/B),which is the highest temperature at which a sample begins to exhibit abrittle mode of failure rather than a ductile mode of failure, wasobtained according to the procedures of ASTM D256 and is also listed inTable I. The sample labeled CONTROL was obtained from a polycarbonateresin having an I.V. of from about 0.46 to about 0.49 dl/g and wasprepared without either the acrylate copolymer or any polyolefin.

EXAMPLE 2

The procedure of Example 1 was repeated exactly, except that thepolypropylene was replaced by a polyethylene/polypropylene copolymer,wherein the weight ratio of the polyethylene fraction to thepolypropylene fraction was about 3 to 2. In the resulting compositionthe weight parts of polycarbonate, acrylate copolymer andpolyethylene/polypropylene copolymer were, respectively, 96, 3 and 1.The results of the notched Izod impact tests and the D/B are listed inTable 1.

EXAMPLE 3

The procedure of Example 2 was repeated exactly, except that the weightparts of polycarbonate, acrylate copolymer andpolyethylene/polypropylene copolymer in the test specimen were,respectively, 97, 2 and 1. The results of the notched Izod impact testsand the D/B are listed in Table 1.

EXAMPLE 4

The procedure of Example 1 was repeated exactly, except that thecomposition contained 94 parts polycarbonate, 4 parts acrylate copolymerand 2 parts polypropylene. The results of the notched Izod impact testsare listed in Table 1.

EXAMPLE 5

The procedure of Example 2 was repeated exactly, except that the weightparts of polycarbonate, acrylate copolymer andpolyethylene/polypropylene copolymer in the test specimen were,respectively, 95, 4 and 1. The results of the notched Izod impact testsand the D/B are listed in Table 1.

EXAMPLE 6

The procedure of Example 1 was repeated exactly, except thatpolypropylene was replaced by polyethylene. The weight parts ofpolycarbonate, acrylate copolymer and polyethylene in the test specimenwere, respectively, 95, 4 and 1. The results of the notched Izod impacttests and the D/B are listed in Table 1.

EXAMPLE 7

The procedure of Example 6 was repeated exactly, except that the weightparts of polycarbonate, acrylate copolymer and polyethylene in the testspecimen were, respectively, 96, 3 and 1. The results of the notchedIzod tests and the D/B are listed in Table 1.

EXAMPLE 8

The procedure of Example 1 was repeated exactly except thatpolypropylene was replaced by polyethylene oxide. The weight parts ofpolycarbonate, acrylate copolymer and polyethylene oxide in the testspecimen were, respectively, 95.5, 4 and 0.5. The results of the notchedIzod impact tests and the D/B are listed in Table 1.

COMPARATIVE EXAMPLE 1

The procedure of Example 5 was repeated exactly, except that theacrylate copolymer was not added to the mixture. The resultingcomposition contained 96 parts polycarbonate and 4 parts polyethylene.The results of the notched Izod impact test and the D/B are listed inTable 1.

COMPARATIVE EXAMPLE 2

The procedure of Comparative Example 1 was repeated exactly, except thatthe composition contained 95 parts polycarbonate and 5 partspolyethylene. The results of the notched Izod impact tests are listed inTable 1.

                                      TABLE I                                     __________________________________________________________________________                Impact Strength, ft. lb./in.                                                  1/4" Thick                                                                          1/8" Thick                                                                          1/8", Heat Aged at 125° C.                                                         D/B, °C.                           Composition of:                                                                           Not Aged                                                                            Not Aged                                                                            24 hrs.                                                                             48 hrs.                                                                             1/8", Not Aged                            __________________________________________________________________________    Example 1   14.1.sup.1                                                                          *     13.4.sup.1                                                                          12.8.sup.1                                                                          -23/-29**                                 Example 2   12.7.sup.1                                                                          *     13.9.sup.1                                                                          13.9.sup.1                                                                          -18/-20**                                 Example 3   13.3.sup.1                                                                          *     13.1.sup.1                                                                          12.1.sup.1                                                                          -18/20**                                  Example 4   *     13.4.sup.1                                                                          13.4.sup.1                                                                          *     *                                         Example 5   14.1.sup.1                                                                          14.1.sup.1                                                                          13.4.sup.1                                                                          13.7.sup.1                                                                          -23/-26**                                 Example 6   13.2.sup.1                                                                          13.3.sup.1                                                                          12.7.sup.1                                                                          12.0.sup.1                                                                          -23/-26**                                 Example 7   12.4.sup.1                                                                          *     13.7.sup.1                                                                          *     -20/-23**                                 Example 8   13.8.sup.1                                                                          *     12.0.sup.1                                                                          10.0.sup.1                                                                          *                                         Comparative Example 1                                                                     11.4.sup.1                                                                          15.0.sup.1                                                                          4.6.sup.1                                                                           *     -15/-18**                                 Comparative Example 2                                                                      8.4.sup.1                                                                          12.5.sup.1                                                                          7.0.sup.3                                                                           *     *                                         CONTROL      1.6.sup.2                                                                          14.8.sup.1                                                                          1.3.sup.2                                                                           *     >-5                                       __________________________________________________________________________     .sup.1 Samples failed with 100% ductility.                                    .sup. 2 Samples failed with 0% ductility.                                     .sup.3 Samples failed with 50% ductility.                                     Test not made.                                                                **Change from ductile mode of failure to brittle mode of failure noted        over indicated range.                                                    

EXAMPLE 9

The procedure of Example 1 was followed exactly, and the resultingcomposition, which contained 95 weight parts polycarbonate, 4 weightparts acrylate copolymer and 1 weight part polypropylene was tested,using the notched Izod test, for subzero temperature impact performanceof 1/8" thick samples which were each maintained at -18° C. and -29° C.for 45 minutes.

EXAMPLE 10

The procedure of Example 6 was followed exactly, and the resultingcomposition, which contained 95 weight parts polycarbonate, 4 weightparts acrylate copolymer and 1 weight part polyethylene was tested,using the notched Izod test, for subzero temperature in the same methodas used for Example 9 above.

The results of these tests, as expressed in ft. lb./in., are set forthin Table II. The results of these tests illustrate the excellent lowtemperature impact strength of the invention's ternary composition.

COMPARATIVE EXAMPLE 3

The procedure of Example 9 was followed except that the polypropylenewas not added to the mixture. The resulting composition, which contained96 weight parts polycarbonate and 4 weight parts acrylate copolymer, wastested for subzero temperature impact performance of a 1/8" thick sampleat -18° C. and -29° C. The results of these tests are set forth in TableII.

                  TABLE II                                                        ______________________________________                                                        Impact Strength, ft. ib./in.                                                  1/8" Thick at                                                 Composition of:   -18° C.                                                                           -29° C.                                   ______________________________________                                        Example 9         12.8       5.0                                              Example 10        12.6       4.0                                              Comparative Example 3                                                                           4.0        2.6                                              ______________________________________                                    

The invention's ternary compositions also exhibited good weldlinestrength as shown in double gate Izod impact tests which were conductedto procedures as specified in ASTM D256.

What is claimed is:
 1. A ternary polycarbonate composition comprising inadmixture, a high molecular weight aromatic polycarbonate which is basedon a dihydric phenol, a minor amount of an acrylate copolymer, which isa copolymer of a C₁ -C₅ acrylate and a C₁ -C₅ methacrylate, and a minoramount of polyethylene oxide.
 2. The composition of claim 1 wherein, inthe acrylate copolymer, the methacrylate is selected from the groupconsisting of methyl methacrylate, 1,3-butylene dimethacrylate, isobutylmethacrylate, butyl methacrylate and ethyl methacrylate and the acrylateis selected from the group consisting of 1,4-butanediol diacrylate,isobutyl acrylate, methyl acrylate, ethyl acrylate, n-butyl acrylate and1,3-butylene diacrylate.
 3. The composition of claim 2 wherein thearomatic polycarbonate is derived from 2,2-bis(4-hydroxyphenyl)propane.4. The composition of claim 3 wherein, in the acrylate copolymer, themethacrylate is methyl methacrylate and the acrylate is n-butylacrylate.
 5. The composition of claim 4 wherein, in the acrylatecopolymer, the weight ratio of methyl methacrylate to n-butyl acrylateranges from about 1/2 to about 2/1.